Prognostic Significance of Monocytic-like Phenotype in AML patients treated with Venetoclax and Azacytidine

• Flow cytometry enhances morphological analysis to detect AML blasts with monocytic differentiation (mono-blasts).

• A high mono-blasts/CD45+ proportion cells predicts poor response and reduced survival in newly diagnosed AML patients receiving Ven-Aza

The prognostic impact of monocytic differentiation in AML patients receiving Venetoclax (Ven) and azacitidine (Aza) remains unclear. In a prospective cohort of 86 newly diagnosed AML patients treated with Ven-Aza, we used multiparametric flow cytometry (MFC) to define mono-blasts as AML blasts co-expressing ≥2 monocytic markers (CD4, CD36, CD64) per ELN guidelines. Patients with higher mono-blasts/CD45+ proportions had lower complete response rates (OR=0.24, p=0.005) and significantly shorter overall survival (OS, 4.0 versus 14.9 months, p=0.003). A ≥10% mono-blasts/CD45+ threshold, identified via maximally selected rank statistics, stratified patients into mono-blasthigh (≥10%) and mono-blastlow (<10%) groups. MFC reclassified 20% of FAB non-M4/5 and 15% of FAB M4/5 cases into mono-blasthigh and mono-blastlow groups, respectively. Multivariable analysis confirmed mono-blasthigh status as an independent adverse prognostic factor for OS (HR=1.95, p=0.023), with a particularly strong impact in ELN 2024 favorable-risk patients (HR=2.81, p=0.024). Our findings highlight monocytic differentiation, assessed via MFC, as a key predictor of Ven-Aza resistance and poor survival, independent of genetic classification. Given its availability in routine diagnostics, MFC-based monocytic assessment could improve AML risk stratification and treatment decisions in patients eligible for less intensive therapies.